EP4172041B1 - Method for controlling the angular position of a wheel, in particular a landing gear of an aircraft - Google Patents

Description

Technical area

The present invention relates to the field of angular orientation of a wheel, in particular, of a wheel of a front landing gear of an aircraft.

In known manner, a front landing gear of an aircraft comprises a wheel which can be oriented in order to allow the pilot to move the aircraft in the desired direction when the aircraft is on the ground, in particular, during a taxi phase. Various solutions are known for controlling the orientation of the wheel using documents. EP2591998A1 , US9139295B2 , FR2963606A1 And GB813912A .

As shown in [ Fig.1 ], the front landing gear comprises a wheel W whose angular position ANG is controlled by two cylinders, in particular, a front hydraulic cylinder V1 and a rear hydraulic cylinder V2. To control the angular position ANG, it is known to use a control system SC* comprising a hydraulic module MH, generally comprises a hydraulic pump (not shown) and a servovalve S, in order to respectively issue a forward command COM1* and a rear COM2* control to the front hydraulic cylinder V1 and the rear hydraulic cylinder V2.

The SC* control system includes a CAL* computer configured to receive a set angular position ANGc from the cockpit and an angular position measurement ANGm in order to deduce a control current COM* which is transmitted to the hydraulic module MH, in particular to the servovalve S, to modify the angular position ANG of the wheel W so that it corresponds to the set angular position ANGc.

• une étape de détermination 11 d'un écart angulaire ε entre la mesure de la position angulaire ANGm et la position angulaire de consigne ANGc,
• une première étape de correction proportionnelle B1 de manière à déterminer un premier courant C1* à partir de l'écart angulaire ε,
• une deuxième étape de correction intégrale B2 de manière à déterminer un deuxième courant C2* à partir de l'écart angulaire ε,
• une étape d'addition 12 du premier courant C1* et du deuxième courant C2* de manière à déterminer un courant de commande COM* de la servovalve S et
• une étape de limitation 13 du courant de commande COM* afin limiter la valeur de la somme des courants Cl*, C2* et fournir un courant de commande COM* adapté à la servovalve S.

The CAL* calculator is in the form of a computer system which implements a regulation process which is presented in [ Fig.2 ]. The regulation process includes:

• a step 11 of determining an angular difference ε between the measurement of the angular position ANGm and the set angular position ANGc,
• a first proportional correction step B1 so as to determine a first current C1* from the angular deviation ε,
• a second integral correction step B2 so as to determine a second current C2* from the angular deviation ε,
• a step 12 of adding the first current C1* and the second current C2* so as to determine a control current COM* of the servovalve S And
• a step 13 of limiting the control current COM* in order to limit the value of the sum of the currents Cl*, C2* and provide a control current COM* adapted to the servovalve S.

Such a regulation process is generally efficient. However, with reference to the [ Fig.3 ], during a modification of the set angular position ANGc (curve 3A), OSC oscillations of the control current COM* (curve 3B) intended for the servovalve S were observed as well as pressure variations in the cylinders hydraulics V1, V2 in steady state. In other words, in the absence of modification of the set angular position ANGc, the control current COM* continues to be regulated unintentionally.

In practice, when the angular deviation ε is close to 0, the integral correction B2 is “loaded” periodically. Indeed, a real S servovalve does not have perfect characteristics. When receiving a low but non-zero COM* control current, the servovalve S does not activate. As a result, the angular deviation ε is not modified and the control current COM* will increase. When the control current COM* becomes strong enough to control the servovalve S, it activates and the angular deviation ε quickly changes sign then returns close to 0. This periodic phenomenon is at the origin of the OSC oscillations of the COM* control current intended for the servovalve S as well as pressure variations in the hydraulic cylinders V1, V2 in steady state.

An immediate solution to eliminate this drawback is to change the servovalve S in order to obtain a more efficient model in terms of regulation when the angular deviation ε is close to 0. In practice, such a change leads to numerous drawbacks as well both technically (integration, certification, etc.) and economically (cost).

Another immediate solution would be to deactivate the integral correction to limit OSC oscillations but this would lower the regulation performance (static error) and the wear monitoring performance of the servovalve S (drift at zero flow, etc.).

The invention thus aims to eliminate at least some of these disadvantages by proposing a new regulation method which eliminates at least some of these disadvantages.

The invention also relates to an aircraft comprising a landing gear as presented previously.

PRESENTATION OF THE INVENTION

• une étape de détermination d'un écart angulaire entre une mesure de la position angulaire et une position angulaire de consigne,
• une première étape de correction proportionnelle de manière à déterminer un premier courant à partir de l'écart angulaire
• une deuxième étape de correction intégrale de manière à déterminer un deuxième courant à partir de l'écart angulaire et
• une étape d'addition du premier courant et du deuxième courant de manière à déterminer un courant de commande de la servovalve .

The invention relates to a method for regulating the angular position of a wheel, in particular a wheel of an aircraft landing gear, the wheel being connected to minus one hydraulic cylinder controlled by a servovalve, the method comprising:

• a step of determining an angular difference between a measurement of the angular position and a set angular position,
• a first proportional correction step so as to determine a first current from the angular deviation
• a second integral correction step so as to determine a second current from the angular deviation and
• a step of adding the first current and the second current so as to determine a control current of the servovalve.

The invention is remarkable in that the second integral regulation step comprises a sub-step of limiting the second current according to a parametric law, the parametric law imposing a second current of zero value when the angular deviation is lower, in absolute value , at a first determined angular threshold.

Advantageously, thanks to the invention, the integral correction step is inhibited only for small angular deviations, that is to say, less than the first determined angular threshold. This makes it possible to avoid a correction by the integral branch which is untimely and which leads to a modification of the pressure of the cylinders. Real faults linked to the servovalve are thus eliminated without modifying the physical architecture, thus avoiding certification steps. In addition, as the integral correction is inhibited occasionally, it continues to be mainly active when the angular position of the wheel is modified. Regulation thus remains optimal and undesirable effects are eliminated.

According to one aspect of the invention, the parametric law limits the second current to a maximum authorized current value when the angular deviation is included, in absolute value, between a second determined angular threshold and a third determined angular threshold, the second threshold determined angular threshold and the third determined angular threshold being greater than the first determined angular threshold. The value of the second current is thus limited during a modification of the set angular position.

According to one aspect of the invention, the parametric law limits the second current according to an ascending ramp between the zero value and the maximum current value authorized when the angular deviation is included, in absolute value, between the first determined angular threshold and the second angular threshold determined.

According to one aspect of the invention, the parametric law limits the second current according to a descending ramp between the maximum authorized current value and zero value when the angular deviation is included, in absolute value, between the third determined angular threshold and a fourth determined angular threshold greater than third threshold determined.

The transitions (ascending or descending) are thus controlled to limit the second current.

• déterminer un écart angulaire entre une mesure de la position angulaire et une position angulaire de consigne,
• réaliser une première correction proportionnelle de manière à déterminer un premier courant à partir de l'écart angulaire
• réaliser une deuxième correction intégrale de manière à déterminer un deuxième courant à partir de l'écart angulaire,
• additionner le premier courant et le deuxième courant de manière à déterminer un courant de commande de la servovalve et
• lors de la réalisation de la deuxième correction intégrale, limiter le deuxième courant selon une loi paramétrique, la loi paramétrique imposant un deuxième courant de valeur nulle lorsque l'écart angulaire est inférieur, en valeur absolue, à un premier seuil angulaire déterminé.

The invention also relates to a system for controlling the angular position of a wheel, in particular of a wheel of an aircraft landing gear, connected to at least one hydraulic cylinder controlled by a servovalve, the system control comprising a computer configured to:

• determine an angular difference between a measurement of the angular position and a set angular position,
• carry out a first proportional correction so as to determine a first current from the angular deviation
• carry out a second integral correction so as to determine a second current from the angular deviation,
• add the first current and the second current so as to determine a control current of the servovalve and
• when carrying out the second integral correction, limit the second current according to a parametric law, the parametric law imposing a second current of zero value when the angular deviation is less, in absolute value, than a first determined angular threshold.

The invention further relates to an assembly of a wheel, in particular a wheel of an aircraft landing gear, connected to at least one hydraulic cylinder controlled by a servovalve and a control system such as presented previously to determine a control current of the servovalve.

Preferably, the wheel is connected to at least a first hydraulic cylinder and a second hydraulic cylinder controlled by the servovalve.

Preferably, the assembly comprises a hydraulic module, comprising the servovalve, configured to directly control the first hydraulic cylinder and the second hydraulic cylinder.

The invention also relates to a landing gear of an aircraft comprising an assembly as presented previously.

PRESENTATION OF FIGURES

• [Fig.1] La [Fig.1] est une représentation schématique d'un système de contrôle de la position angulaire d'une roue d'un train d'atterrissage avant selon l'art antérieur.
• [Fig.2] La [Fig.2] est une représentation schématique des étapes d'un procédé de régulation de la position angulaire selon l'art antérieur.
• [Fig.3] La [Fig.3] est une représentation schématique de l'évolution temporelle d'une position angulaire de consigne et du courant de commande de la servovalve selon l'art antérieur.
• [Fig.4] La [Fig.4] est une représentation schématique d'un système de contrôle de la position angulaire d'une roue d'un train d'atterrissage avant selon une forme de réalisation de l'invention.
• [Fig.5] La [Fig.5] est une représentation schématique des étapes d'un procédé de régulation de la position angulaire selon un exemple de mise en oeuvre.
• [Fig.6] La [Fig.6] est une représentation schématique d'une loi paramétrique pour la limitation du deuxième courant issu de la correction intégrale.
• [Fig.7] La [Fig.7] est une représentation schématique de l'évolution temporelle d'une position angulaire de consigne, de l'écart angulaire et du courant de commande de la servovalve selon l'invention.

The invention will be better understood on reading the description which follows, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects .

• [ Fig.1 ] There [ Fig.1 ] is a schematic representation of a system for controlling the angular position of a wheel of a front landing gear according to the prior art.
• [ Fig.2 ] There [ Fig.2 ] is a schematic representation of the steps of a process for regulating the angular position according to the prior art.
• [ Fig.3 ] There [ Fig.3 ] is a schematic representation of the temporal evolution of a set angular position and the control current of the servovalve according to the prior art.
• [ Fig.4 ] There [ Fig.4 ] is a schematic representation of a system for controlling the angular position of a wheel of a front landing gear according to one embodiment of the invention.
• [ Fig.5 ] There [ Fig.5 ] is a schematic representation of the steps of a method for regulating the angular position according to an example of implementation.
• [ Fig.6 ] There [ Fig.6 ] is a schematic representation of a parametric law for the limitation of the second current resulting from the integral correction.
• [Fig.7] [Fig.7] is a schematic representation of the temporal evolution of a set angular position, the angular deviation and the control current of the servovalve according to the invention.

It should be noted that the figures set out the invention in detail to implement the invention, said figures being able of course to be used to better define the invention if necessary.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a system for controlling the angular position of a wheel, in particular a wheel of a front landing gear of an aircraft. In known manner, a front landing gear of an aircraft comprises a wheel which can be oriented in order to allow the pilot to move the aircraft in the desired direction when the aircraft is on the ground, in particular, during a taxi phase.

With reference to the [ Fig.4 ], as presented previously, the front landing gear comprises a wheel W whose angular position ANG is controlled by two cylinders, in particular, a front hydraulic cylinder V1 and a rear hydraulic cylinder V2.

According to the invention, to control the angular position ANG, a control system SC is used comprising a hydraulic module MH, which comprises a hydraulic pump (not shown) and a servovalve S, in order to respectively issue a forward command COM1 and a rear control COM2 to the front hydraulic cylinder V1 and to the rear hydraulic cylinder V2.

The control system SC includes a computer CAL configured to receive a set angular position ANGc from the cockpit and an angular position measurement ANGm in order to deduce a control current COM which is transmitted to the hydraulic module MH, in particular to the servovalve S, to modify the angular position ANG of the wheel W so that it corresponds to the angular position ANGc setpoint.

According to the invention, the CAL calculator is in the form of a computer system which implements a regulation method which is presented in [ Fig.5 ].

First of all, the regulation method comprises a step E1 of determining an angular difference ε between a measurement of the angular position ANGm and the set angular position ANGc.

Then, the regulation method comprises a first proportional correction step R1 so as to determine a first current C1 from the angular deviation ε. With reference to the [ Fig.5 ], during the proportional correction step R1, the angular deviation ε is multiplied by a first constant Kp so as to deduce a first current C1 which has previously been limited in value by a limitation operator L1. Preferably, the first proportional correction step R1 is analogous to the prior art and will not be presented in further detail.

The regulation method comprises a second integral correction step R2 so as to determine a second current C2 from the angular deviation ε.

A control current COM of the servovalve S is then determined during an addition step E2 of the first current C1 and the second current C2. The control current COM is limited in value by a limitation operator L2 following the addition of the first current C1 and the second current C2.

The second step of integral correction R2 will now be presented in detail. This includes a sub-step R2' of integration of the angular deviation ε with a second constant Ki in order to obtain the second current C2. Preferably, during the integration sub-step R2' of the angular deviation ε, an activation/deactivation of the integration is carried out if the deviation ε, in absolute value, is between 0 and one predetermined threshold, 2° in this example.

During the integration sub-step R2', the second current C2 is previously limited in value by a limitation operator L3 in order to form the control current COM. The integration sub-step is analogous to the prior art and will not be presented in more detail.

Preferably, according to the invention, the second integral regulation step R2 comprises a sub-step of limitation (R2") of the second current C2 according to a parametric law LP. Unlike a conventional limitation which aims to limit extreme values, this parametric law LP is defined to avoid any oscillatory phenomenon.

The parametric law LP determines a value of the second current C2 as a function of the absolute value of the angular deviation ε. With reference to the [ Fig.6 ], several determined angular thresholds of increasing value ε1, ε2, ε3, ε4 are defined. The angular thresholds are determined according to the needs of the regulation (speed, precision, error static, etc.).

When the angular deviation ε is less, in absolute value, than the first determined angular threshold ε1, that is to say between 0 and ε1, the parametric law LP imposes a second current C2 of zero value. Such cancellation of the second current C2 makes it possible to eliminate all oscillations by preventing the integral correction from “charging” intermittently. No current command C2 is sent to the servovalve to control the cylinders V1, V2 whose hydraulic pressure does not vary, the proportional part C1 only canceling if the difference is zero. Any oscillatory phenomenon is eliminated without replacing the servovalve S or the cylinders V1, V2.

When the angular difference ε is included, in absolute value, between the second determined angular threshold ε2 and the third determined angular threshold ε3, the second current C2 is limited to a maximum authorized current value C2max in order to limit the value of the second current C2 and protect the servovalve S.

When the angular difference ε is included, in absolute value, between the first determined angular threshold ε1 and the second determined angular threshold ε2, the second current C2 is limited according to an ascending ramp between the zero value and the maximum authorized current value C2max. Likewise, when the angular difference ε is included, in absolute value, between the third determined angular threshold ε3 and the fourth determined angular threshold ε4, the second current C2 is limited according to a descending ramp comprised between the maximum authorized current value C2max and the value zero. The ramps advantageously make it possible to ensure a `smooth' variation when the deviation ε passes below the second determined angular threshold ε2 or above the third determined angular threshold ε3 during the control.

Thus, the second integral correction R2 remains active and is only inhibited when the angular deviation ε is too small to be perceived by the servovalve S. Advantageously, the value of the first determined angular threshold ε1 can be adapted to obtain the desired regulation .

• déterminer un écart angulaire ε entre une mesure de la position angulaire ANGm et une position angulaire de consigne ANGc,
• réaliser une première correction proportionnelle R1 de manière à déterminer un premier courant C1 à partir de l'écart angulaire ε
• réaliser une deuxième correction intégrale R2 de manière à déterminer un deuxième courant C2 à partir de l'écart angulaire ε,
• additionner le premier courant C1 et le deuxième courant C2 de manière à déterminer un courant de commande COM de la servovalve S,
• lors de la réalisation de la deuxième correction intégrale R2, limiter le deuxième courant C2 selon une loi paramétrique, la loi paramétrique imposant un deuxième courant C2 de valeur nulle lorsque l'écart angulaire ε est inférieur, en valeur absolue, à un premier seuil angulaire déterminé ε1.

The CAL computer is configured to implement the steps of the regulation process, in particular, for:

• determine an angular difference ε between a measurement of the angular position ANGm and a set angular position ANGc,
• carry out a first proportional correction R1 so as to determine a first current C1 from the angular deviation ε
• carry out a second integral correction R2 so as to determine a second current C2 from the angular deviation ε,
• add the first current C1 and the second current C2 so as to determine a control current COM of the servovalve S,
• when carrying out the second integral correction R2, limit the second current C2 according to a parametric law, the parametric law imposing a second current C2 of zero value when the angular deviation ε is less, in absolute value, than a first determined angular threshold ε1.

Advantageously, it is enough to modify the regulation method implemented by a CAL computer to benefit from the benefits of the invention, without any other physical material change.

With reference to [Fig.7], during the implementation of the regulation process, during a modification of the set angular position ANGc (curve 7A), the angular deviation ε is canceled when it is lower first determined angular threshold ε1 and does not exhibit oscillation (curve 7B). As a result, the control current COM (curve 7C) is also devoid of oscillations OSC. There are thus no undesirable pressure variations in the hydraulic cylinders V1, V2 in steady state. In other words, in the absence of modification of the set angular position ANGc, the control current COM is no longer corrected unintentionally.

Claims (10)

1. Method for adjusting the angular position (ANG) of a wheel (W), in particular of a wheel of an aircraft landing gear, the wheel (W) being connected to at least one hydraulic cylinder controlled by a servo valve (S), the method comprising:

   - a step of determining (E1) an angular difference (ε) between a measurement of the angular position (ANGm) and a setpoint angular position (ANGc),

   - a first proportional correction step (R1) so as to determine a first current (C1) from the angular difference (ε)

   - a second integral correction step (R2) so as to determine a second current (C2) from the angular difference (ε),

   - a step of adding (E2) the first current (C1) and the second current (C2) so as to determine a control current (COM) of the servo valve (S)

   - method characterised in the fact that,

   - the second integral adjustment step (R2) comprises a substep of limiting (R2") the second current (C2) according to a parametric law (LP), the parametric law (LP) imposing a zero-value second current (C2) when the angular difference (ε) is less, in absolute value, than a determined first angular threshold (ε1).
2. Method for adjusting according to claim 1, wherein the parametric law (LP) limits the second current (C2) to a maximum permissible current value (C2max) when the angular difference (ε) is comprised, in absolute value, between a second determined angular threshold (ε2) and a third determined angular threshold (ε3), the second determined angular threshold (ε2) and the third determined angular threshold (ε3) being greater than the first determined angular threshold (ε1).
3. Method for adjusting according to claim 2, wherein the parametric law (LP) limits the second current (C2) according to a rising ramp comprised between the zero value and the maximum permissible current value (C2max) when the angular difference (ε) is comprised, in absolute value, between the first determined angular threshold (ε1) and the second determined angular threshold (ε2).
4. Method for adjusting according to one of claims 2 and 3, wherein the parametric law (LP) limits the second current (C2) according to a falling ramp comprised between the maximum permissible current value (C2max) and the zero value when the angular difference (ε) is comprised, in absolute value, between the third determined angular threshold (ε3) and a fourth determined angular threshold (ε4) greater than the third determined threshold (ε3).
5. System for controlling (SC) the angular position of a wheel (W), in particular of a wheel of an aircraft landing gear, connected to at least one hydraulic cylinder (V1, V2) controlled by a servo valve (S), the control system (SC) comprising a calculator (CAL) configured to:

   - determine an angular difference (ε) between a measurement of the angular position (ANGm) and a setpoint angular position (ANGc),

   - perform a first proportional correction (R1) in order to determine a first current (C1) from the angular difference (ε)

   - perform a second integral correction (R2) so as to determine a second current (C2) from the angular difference (ε),

   - add the first current (C1) and the second current (C2) so as to determine a control current (COM) of the servo valve (S) and

   - when performing the second integral correction (R2), limit the second current (C2) according to a parametric law (LP), the parametric law (LP) imposing a zero-value second current (C2) when the angular difference (ε) is less, in absolute value, than a first determined angular threshold (ε1).
6. Assembly of a wheel (W), in particular a wheel of an aircraft landing gear, connected to at least one hydraulic cylinder (V1, V2) controlled by a servo valve (S) and a control system (SC) according to claim 5 to determine a control current (COM) of the servo valve (S).
7. Assembly according to claim 6, wherein the wheel (W) is connected to at least one first hydraulic cylinder (V1) and a second hydraulic cylinder (V2) controlled by the servo valve (S).
8. Assembly according to one of claims 6 and 7 comprising a hydraulic module (MH), comprising the servo valve (S), configured to directly control the first hydraulic cylinder (V1) and the second hydraulic cylinder (V2).
9. Aircraft landing gear comprising an assembly according to one of claims 6 to 8.
10. Aircraft comprising a landing gear according to claim 9.

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